Useful Website for Children to Learn Chess

Lichess is great for playing and learning you just need to ensure that you select the Child option rather than the adult one when setting up the account. This is very important and will keep your child safe.

https://lichess.org/

Kids chess is also great and the free membership allows you to enjoy some of the features (but the paid version is recommended if your child is serious about chess):

https://www.chesskid.com/

The Exeter Chess website is an excellent one and probably the best single place to get free material on the web: